Apparatus having an electrical machine

ABSTRACT

An apparatus such as a vehicle having a generator. The apparatus includes a rotational shaft having a longitudinal axis, a stator having a core and windings disposed on the core, and a rotor coupled to the shaft. The core includes first and second surfaces at least partially surrounding the longitudinal axis. A portion of the first inner surface is disposed a first radial distance from the longitudinal axis, and a portion of the second inner surface is disposed a second radial distance from the longitudinal axis. The second radial distance is greater than the first radial distance.

RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 09/835,889,filed Apr. 16, 2001 now U.S. Pat. No. 6,603,227.

BACKGROUND OF THE INVENTION

The invention relates to a vehicle including a generator and,particularly, to a vehicle including a generator that provides a120-VRMS, 60-Hz power source.

Small mobile generators are capable of providing a stable 120-Voltsroot-mean-square (VRMS), 60-Hertz (Hz) power source. In addition,because the generators are mobile, the generators may be transported tothe desired location where electrical power is needed. However, mobilegenerators are usually placed on a trailer and pulled to the desiredlocation by a vehicle.

Small-engine vehicles, such as riding lawn mowers, tractors, all-terrainvehicles (ATV's), golf carts, etc., are robust vehicles capable oftravelling to remote locations. Small-engine vehicles are also able topull small mobile generators. However, when the desired location for thegenerator is in a remote location or across a treacherous landscape, itmay be difficult for the small-engine vehicle to pull the trailercarrying the generator to the desired location.

When an operator owns a small-engine vehicle and a mobile generator, theoperator's costs increase. In addition, the operator is required tomaintain two pieces of machinery (e.g., maintain two engines). This maynot be practical when the mobile generator is infrequently used.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a vehicle including a plurality ofwheels, an internal combustion engine having a drive shaftinterconnected to drive at least one of the wheels, and a generator. Thegenerator includes a stator having a core disposed next to the engineand a winding disposed on the core. The generator further includes aflywheel-rotor apparatus surrounding at least a portion of the statorand having an aperture that receives the drive shaft. The flywheel-rotorapparatus is operable to magnetically interact with the stator toproduce a first high-voltage, alternating-current signal in the winding,and to provide inertia to the internal combustion engine. The generatorfurther includes power circuitry electrically connected to the winding.The power circuitry receives the high-voltage, alternating-currentsignal and controllably generates a second high-voltage,alternating-current signal. The power circuitry includes a regulatorthat regulates the first high-voltage, alternating-current signal to ahigh-voltage, direct-current signal, a storage device that stores thehigh-voltage, direct-current signal, and an inverter that converts thehigh-voltage, direct-current signal to the second high-voltage,alternating-current signal.

The generator of the engine is capable of being retrofitted ontoexisting vehicles. For vehicles having a limited engine compartmentvolume, the invention provides a generator having a stator, including atleast one recess that receives at least a portion of an engine housing.That is, the invention further provides a stator including alongitudinal axis and a core. The core includes a first inner surface atleast partially surrounding the longitudinal axis, and a second innersurface at least partially surrounding the longitudinal axis. The secondinner surface is adjacent to the first inner surface in an axialdirection, and the second inner surface at least partially defines arecess. The recess extends in a circumferential direction with respectto the engine housing of the generator. However, although the core isdescribed in connection with a vehicle, the core may be used with othergenerators and even other motors.

The generator of the invention includes a first winding that generates afirst high-voltage AC signal (e.g., a voltage greater than 200-Voltspeak-to-peak). The first winding is isolated from a second winding. Thesecond winding may produce a low-voltage signal for storing power on abattery and/or for powering the ignition system.

Thus, in another aspect of the invention, the invention provides agenerator including an engine having a shaft, a rotor interconnectedwith the shaft, and a stator. The stator includes a core having aplurality of teeth that receive wire where the teeth are numberedconsecutively from (1) to (x). The stator further includes a first wiredisposed on the core to form a first group of coils. The first group ofcoils forms at least two poles numbered consecutively from (1) to (x−n)with each pole being formed on a respective tooth. The first wireincludes first and second ends that exit the core between two adjacentteeth receiving the first group of coils. The stator further includes asecond wire disposed on the core to form a second group of coils. Thesecond group of coils forms at least two poles numbered consecutivelyfrom (x−n+1) to (x) with each pole being formed on a respective tooth.The second wire has third and fourth ends that exit the core between twoadjacent teeth receiving the second group of coils.

The invention further provides a method of winding a stator for agenerator. The method includes the step of providing a core including aplurality of teeth formed in the core. The teeth being numberedconsecutively from (1) to (x) and receiving wire. The method furtherincludes the step of disposing a first wire having first and second endson the core to form a first group of coils. The disposing of the firstwire includes forming at least two poles numbered consecutively from (1)to (x−n) on respective teeth. The forming of at least two poles includesforming the odd numbered poles of the first group in a first directionand forming the even numbered poles of the first group in a seconddirection different than the first direction. The disposing or windingof the first wire further includes exiting the first and second endsbetween two adjacent teeth receiving the first group of coils. Themethod further includes the step of disposing or winding a second wirehaving third and fourth ends on the core to form a second group ofcoils. The disposing of the second wire includes forming at least twopoles numbered consecutively from (x−n+1) to (x) on respective teeth.The forming of at least two poles includes forming the odd numberedpoles of the second group in the first direction and forming the evennumbered poles of the second group in the second direction. Thedisposing of the second wire further includes exiting the first andsecond ends between two adjacent teeth receiving the second group ofcoils.

Other features and advantages of the invention are set forth in thefollowing detailed description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicle embodying the invention.

FIG. 2 is a partial side view of an engine and generator combinationembodying the invention.

FIG. 3 is a partial perspective view of a stator and an engine housingshown in FIG. 2.

FIG. 4 is a plan view of a first stator viewed from a front side.

FIG. 5 is a plan view of a first stator viewed from a rear side.

FIG. 6 is a plan view of a second stator viewed from a rear side.

FIG. 7 is a plan view of a third stator viewed from a rear side.

FIG. 8 is a plan view of a fourth stator viewed from a rear side.

FIG. 8(a) is a cross-sectional side view of the stator taken along line8A—8A in FIG. 8.

FIG. 9 is a schematic representation of a stator-winding scheme.

FIG. 10 is a plan view of a flywheel-rotor apparatus from the rear.

FIG. 11 is a cross-sectional side view of the flywheel-rotor apparatustaken along line 11—11 in FIG. 10.

FIG. 12 is a schematic diagram of power circuitry schematically shown inFIG. 1.

FIG. 13 is an electrical schematic of a regulator schematically shown inFIG. 12.

FIG. 14 is an electrical schematic of a bridge circuit schematicallyshown in FIG. 12.

FIG. 15 is an electrical schematic of a first driver circuitschematically shown in FIG. 12.

FIG. 16 is an electrical schematic of a second driver circuitschematically shown in FIG. 12.

FIG. 17 is an electrical schematic of a current limit circuitschematically shown in FIG. 12.

FIG. 18 is an electrical schematic of a microprocessor, a voltagefeedback circuit, a thermal shutdown circuit, and a voltage regulatorschematically shown in FIG. 12.

FIG. 19 is a flow chart of a software program.

FIGS. 20(a) and 20(b) are flow charts of an interrupt service step shownin FIG. 19.

Before any embodiments of the invention are explained in full detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of components setforth in the following description or illustrated in the followingdrawings. The invention is capable of other embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including” and “comprising” and variations thereof herein is meantto encompass the items listed thereafter and equivalents thereof as wellas additional items.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A vehicle 100 embodying the invention is schematically shown in FIG. 1.The vehicle 100 includes a plurality of wheels 105 and an internalcombustion engine 110 (hereinafter referred to as “engine”)interconnected to drive at least one of the wheels 105. That is, theengine 110 (also shown in FIG. 2) produces mechanical power causing ashaft 115 to rotate. One or more wheels 105 are interconnected with therotating shaft 115 causing the interconnected wheels 105 to rotate. Forthe embodiment described herein, the vehicle 100 is a riding lawnmowerwith a Briggs & Stratton, Inc. INTEK™ or DBS™ engine. However, thevehicle 100 may be any vehicle including a small-engine (e.g., atractor, a lawnmower, an ATV, a golf cart, a motorcycle, etc.)

The vehicle 100 further includes an alternator or generator 120interconnected with the engine 110. In general, the generator 120includes a flywheel-rotor apparatus 125 (FIG. 2), a stator 130 (FIG. 2),power circuitry 135 (FIG. 1) and an electrical outlet 140 (FIG. 1). Asshown in FIG. 2 and shown in partial perspective view FIG. 3, the engineincludes a housing 145, and the stator 130 is mounted to the housing 145by one or more fasteners (discussed below).

As shown in FIGS. 3, 4 and 5, the stator 130 includes a magneticallypermeable stator core 150, which is of generally cylindrical shape. Thecore 150 is formed by a plurality of stacked laminations 155 (best shownin FIG. 3) mechanically interconnected together by one or more fasteners160. Alternatively, the core 150 may be a solid core formed by onemagnetically permeable member or may be magnetic powdered materialcompressed to form the core 150. The one or more fasteners 160 mayinclude rivets, bolts, latches, etc., or even an epoxy or glue. In theembodiment shown, the core 150 includes a first plurality of laminations165 (best shown in FIGS. 3 and 5) and a second plurality of laminations170 (best shown in FIGS. 3 and 5) fastened by four rivets 160 (bestshown in FIG. 3).

The stator 130 includes a central opening 175 having a longitudinal axis180 (best shown in FIGS. 4 and 5). The stator 130 is mounted on theengine housing 145 such that the central opening 175 receives at least aportion of the shaft 115. The stator 130 is secured to the housing 145by one or more fasteners (e.g., rivet, bolt, latch, epoxy, glue, etc.)185.

The stator core 150 forms at least one inner surface at least partiallysurrounding the longitudinal axis 180. For the embodiment shown and withreference to FIG. 5, the first plurality of laminations 165 form a firstinner surface 190 surrounding the longitudinal axis 180, and the secondplurality of laminations 170 form a second inner surface 195 thatextends in the circumferential direction with respect to thelongitudinal axis 180. The second inner surface 195 is adjacent to thefirst inner surface 190 in the axial direction. The first plurality oflaminations 165 further includes first, second, third and fourth shelves215, 220, 225 and 230, and first, second, third and fourth apertures235, 240, 245 and 250. The first shelf 215 and a portion of the secondinner surface 195 partially define a first recess 255, the second shelf220 and a portion of the second inner surface 195 partially define asecond recess 260, the third shelf 225 and a portion of the second innersurface 195 partially define a third recess 265, and the fourth shelf230 and a portion of the second inner surface 195 partially define afourth recess 270.

The recesses 255, 260, 265 and 270 result in a volume of the stator core150 that is “removed” as compared to a core that has only one pluralityof substantially similarly designed laminations of cylindrical shape(e.g., discussed below). The creation of the recesses 255, 260, 265 and270 allows the recesses 255, 260, 265 and 270 to extend in thecircumferential direction for receiving a portion of the housing 145. Bycreating the recesses 255, 260, 265 and 270, the stator 130 of theinvention maybe retrofitted on existing engines 110 where space is anissue.

For example, the housing 145 of a prior art engine may include astructure that would otherwise result in interference (e.g., ribstructures 275 as shown in FIG. 3). In addition, the amount of enginecompartment volume of the vehicle (i.e., the space “under the hood”) maybe of concern. In order to mount the generator 120 within the existingvolume, the recesses 255, 260, 265 and 270 may be created in the stator130. The recesses 255, 260, 265 and 270 allow one or more structures toextend into the one or more recesses 255, 260, 265 and 270 (e.g., therib structures 275 shown in FIG. 3 extend into the one or more recesses255, 260, 265 and 270.) This allows the stator 130 to sit closer to theengine 110 than if no recess was created.

Furthermore, one or more apertures 235, 240, 245 or 250 may extendthrough recesses 255, 260, 265 and 270, respectively, in thelongitudinal direction. The apertures allow the stator 130 to be mountedcloser to the engine housing 145. Having the stator 130 sit closer tothe engine housing 145 allows for the engine and generator combinationto be more compact and fit within an existing engine compartment volumeof an existing vehicle.

In another embodiment of the invention, the stator core 276 (shown inFIG. 6) does not include one or more recesses. For this embodiment,space is not an issue. Rather, the stator 130 of this embodiment uses a“cylindrical” stator core 276 that generates more power than a corehaving at least one recess (e.g., a core 150 shown in FIG. 5).

In another embodiment of the invention, the second plurality oflaminations partially define one recess 277 that completely surroundsthe longitudinal axis (shown in FIG. 7). In addition, for otherembodiments, the number of recesses may vary and the amount of volume ofa recess may vary.

In another embodiment of the invention, the recess 278 (shown in FIG. 8)is formed by at least three sets of laminations 279A, 279B and 279C.Specifically, the recess 278 is formed by gradually varying the radiusR1, R2 and R3 of at least a portion of each set of laminations in theaxial direction. For another embodiment of the invention, the one ormore recesses may be defined by a solid core. For some solid coreembodiments, the one or more recess are defined by a continuouslyvarying radius in the longitudinal direction.

As best shown in FIG. 3, the stator 130 further includes a plurality ofradially-extending teeth 280 and insulators 295 and 300 disposed on theteeth 280. The teeth 280 receive one or more electrical wires 305 thatsurround the insulators 295 and 300. The insulators 295 and 300electrically isolate the wires 305 from the stator core 150. For theembodiment shown, the insulators 295 and 300 are first and secondplastic insulators disposed on the core 150. Furthermore, for theembodiment shown, the number of teeth, which may be represented by thenumber (x), is equal to eighteen and the number of wires 305 is equal totwo. However, the number of teeth may vary and the number of wires mayvary. For example, in another embodiment of the invention, the number ofteeth is equal to twenty. Changing the number of teeth enables morepower to be generated.

As best shown in FIG. 5, the teeth 280 (FIG. 3) are numbered from 1 to(x) (e.g., 1 to 18). As schematically shown in FIG. 9, a first wire 310is wound around a first plurality of teeth to form a first plurality ofcoils 315. The first plurality of coils 315 create a first plurality ofmagnetic poles that interact with a plurality of magnets (discussedbelow) of the flywheel-rotor apparatus 125. A second wire 320 is woundaround a second plurality of teeth to form a second plurality of coils325. The second plurality of coils 325 create a second plurality ofmagnetic poles that interact with the plurality of magnets (discussedbelow) of the flywheel-rotor apparatus 125.

Specifically, for the embodiment schematically shown in FIG. 9, the core150 includes a plurality of teeth numbered from 1 to 18. The first wire310 is wound on the core 150 to form a first group of coils 315. Thefirst group of coils 315 forms at least sixteen poles numbered 1 to 16with each pole being formed on a respective tooth 1 to 16. The firstwire 310 includes first and second ends 330 and 335 that exit the corebetween two adjacent teeth receiving the first group of coils 315. Forthe embodiment shown, the first and second ends 330 and 335 exit thecore between the first and second teeth. The second wire 320 is disposedon the core 150 to form a second group of coils 325. The second group ofcoils 325 form at two poles numbered 17 and 18 with each pole beingformed on a respective tooth 17 and 18. The second wire 320 includesthird and fourth ends 340 and 345 that exit the core between twoadjacent teeth receiving the second group of coils 325. For theembodiment shown, the third and fourth ends 340 and 345 exit the corebetween the seventeenth and eighteenth teeth.

Although the first group of coils 315 form a first group of poles 1 to16 and the second group of coils 325 form a second group of poles 17 and18, the number of poles of each group may vary. For example, the firstgroup of poles may be numbered from one to (x−n) where (x) is the totalnumber of poles or teeth and (n) is the number of poles in the secondgroup. For the second group, the poles are numbered from (x−n+1) to (x).Thus, for the embodiment shown, (x) is eighteen and (n) is two. Inanother embodiment of the invention, (x) is twenty and (n) is two.

As will be discussed in further detail below, the flywheel-rotorapparatus 125 magnetically interacts with the stator 130 to generate afirst voltage in the first wire 310 and generates a second voltage inthe second wire 320, where the first voltage is greater than the secondvoltage. For example, the first voltage may be greater thanapproximately 200-Volts peak-to-peak, and the second voltage may be lessthan approximately 50-Volts peak-to-peak. The voltage (and power)generated in each wire 310 or 320 is determined in part on the number ofpoles formed by the respective group of coils. In other words, varyingthe number of poles in a group of coils varies the voltage generated bythe group of coils. For example, varying the number of poles for thefirst group of coils 315 from sixteen to eighteen increases the voltagegenerated by the first group of coils 315. Thus, depending on thevoltage required by a group of coils, the number of poles (and teeth)may vary.

In addition, varying the number of turns of each coil also increases thevoltage generated by the group of coils. For example, if the number ofturns for each coil changes from fifteen to twenty, then a highervoltage is generated for the group of coils.

For the winding scheme shown, the first and second ends 330 and 335 exitbetween two adjacent teeth receiving the first group of coils 315 (e.g.,between teeth 1 and 2), and the third and fourth ends 340 and 345 exitbetween two adjacent teeth receiving the second group of coils 325(e.g., between teeth 17 and 18). One reason for this is that undesirablenoise is transmitted from the first and second ends to the third andfourth ends due to the first group of coils generating a much highervoltage than the second group of coils. By having the first and secondends exit between two teeth of the first group of coils and by havingthe third and fourth ends exit between two teeth of the second group ofcoils, the noise is reduced. Although the embodiment described hereinhas the first and second ends exit between the first and second teeth,the first and second ends may exit between two other adjacent teethreceiving the first group of coils. Similarly, if the number of teethreceiving the second group of coils varies (e.g., (n) is equal to 4),then the third and fourth ends may exit between any two adjacent teethreceiving the second group of coils. However, if noise is not a concern,then other winding schemes may be used for the vehicle.

As shown in FIG. 9, the coils forming the odd numbered poles of thefirst group (e.g., poles 1, 3, 5, 7, 9, 11, 13, 15) are wound in a firstdirection (e.g., counterclockwise when viewing the core 150 from therear), and the coils forming the even numbered poles of the first group(e.g., poles 2, 4, 6, 8, 10, 12, 14, 16) are wound in a second direction(e.g., counterclockwise when viewing the core 150 from the rear). Thesecond direction is different than the first direction. Similarly, thecoils forming the odd numbered poles of the second group (e.g., pole 17)are wound in the first direction, and the coils forming the evennumbered poles of the second group (e.g., pole 18) are wound in thesecond direction.

One method of disposing the first and second wires 310 and 320 on thestator 130 is as follows. As schematically shown in FIG. 9, the firstwire 310 is wound on the core 150 to form the first group of coils 315.The first group of coils 315 is formed by placing the first end 310between teeth 1 and 2 and winding the wire around tooth 1 in the firstdirection. Next, the wire 310 is then wound to tooth 2 and a second coilis wound around tooth 2 in the second direction. The wire 310 thenproceeds to tooth 3 and is wound around tooth 3 in the first direction.Next, the wire proceeds to tooth 4 and is wound around tooth 4 in thesecond direction. The winding on the first group of coils 315 is woundsimilarly for the remaining teeth 6-16, where the odd number poles arewound in the first direction and the even number of poles are wound inthe second direction.

After winding the first wire 310 around tooth 16, the second wire 320 iscut to form the second end 330. An insulator 350 (e.g., a “shrink-tube”insulator) (FIG. 3) is disposed around the second end 330 and the firstwire 310 is interwound back to tooth 2. That is, the first wire 310 iswound for a half turn around tooth 16, proceeds to the tooth 15, and iswound a half turn around tooth 15 (FIG. 9). The first wire 310 is woundfor half turns around the remaining teeth back to tooth 2 and exitsbetween teeth 1 and 2. The insulator 350 protects the half-turn windingfrom short-circuiting with the coils of the respective teeth. Forexample, the half-turn winding around tooth 7 does not short circuitwith the coil that forms pole 7. The first and second ends 330 and 335exit between the teeth 1 and 2 receiving the first and second coils. Tostrain relieve the first and second ends 330 and 335, an epoxy 355 (FIG.5) may be applied to ends 330 and 335.

Similar to the first wire 310, the second wire 320 having third andfourth ends 340 and 345 is disposed on the core 150 to form the secondgroup of coils 325. The second group of coils is formed by placing thethird end 340 between tooth 17 and winding the wire around tooth 17 inthe first direction. Next, the second wire 320 is then wound to tooth 18and a second coil is wound around tooth 18 in the second direction.After winding the second wire 320 around tooth 18, the second wire 320is cut to form the fourth end 345. The third and fourth ends 340 and 345then exit between teeth 17 and 18. To strain relieve the third andfourth ends 340 and 345, an epoxy 360 (FIG. 5) may be applied to ends340 and 345.

For the embodiment shown, (n) is equal to two. However, if (n) isgreater than two, then the winding scheme for the second wire 320 may besimilar to the winding scheme for the first wire 310.

Referring back to FIG. 2, the generator 120 further includes aflywheel-rotor apparatus 125 that is coaxially aligned with the stator130. As best shown in FIGS. 10 and 11, the flywheel-rotor apparatus 125includes a first central opening 370 for receiving the drive shaft 115(FIG. 2). When the drive shaft 115 rotates, the flywheel-rotor apparatus125 also rotates. The rotating flywheel-rotor apparatus 125 induces amagnetic field within the stator 130 causing a current to be generatedin each wire 310 and 320.

Referring again to FIGS. 10 and 11, the flywheel-rotor apparatus 125includes a third inner surface 375 at least partially surrounding thestator 130. The flywheel-rotor apparatus 125 further includes aplurality of rotor magnets 380 (e.g., eighteen magnets) mounted byfasteners (e.g., an epoxy or glue) to the third inner surface 375. Inthe embodiment show, the rotor magnets 380 are neodymium-iron-boron(NdFeB) magnets. The flywheel-rotor apparatus 125 further includes anignition magnet 385 mounted in the exterior of the flywheel-rotorapparatus 125 for generating an ignition signal, gearing teeth 390disposed in the exterior of the flywheel-rotor apparatus 125 forinterconnecting the flywheel-rotor apparatus 125 to an engine startingmotor, apertures 395 for receiving a fan plate having fins for coolingthe engine and generator, and one or more balancing holes 400 used forbalancing the flywheel-rotor apparatus 125.

The flywheel-rotor apparatus 125 includes a flywheel portion 402interconnected with a rotor portion 404. The rotor portion 404 includesthe magnets 380 and a back-iron 405. The rotor portion 404 is externalto the stator 130 and magnetically interacts with the stator 130. Theflywheel portion 402 is an additional mass formed integral with therotor portion 404 and may include a portion of the rotor back-iron 405.The flywheel portion 404 evens out the rotation of the drive shaft 115while the engine 110 is running. The additional mass of the flywheelportion 402 is necessary for the internal-combustion engine 110 tooperate properly and the rotor portion 404 is necessary to produce themagnetic field for the generator 120. By combining the flywheel androtor portions 402 and 404 into one apparatus 125, the number of partsis reduced and the amount of space required for the engine/generatorcombination 110 and 120 is reduced.

FIG. 12 shows a schematic diagram of the power circuitry 135, and FIGS.13-18 show an electrical schematic of the power circuitry 135. Withreference to FIGS. 12 and 13, the power circuitry includes a regulator500. As used herein, the regulator 500 receives a high-voltage,alternating-current (AC) input, and rectifies and regulates the receivedalternating current to generate a high-voltage DC output. Thehigh-voltage, AC input is received at terminals W3 and W9 from first andsecond ends 330 and 335. For the embodiment described herein, thelow-voltage DC output is approximately 15-VDC and the high-voltage DCoutput is approximately 150-VDC. However, the low-voltage andhigh-voltage DC output voltages may vary. Even further, for theembodiment described, the high-voltage DC signal may vary depending onthe load attached to the power circuitry 135.

The high-voltage AC input may be a single-phase AC input generated bythe above-described stator 130, may be a single-phase AC input generatedby another stator, or a three-phase AC input generated by a statorhaving three-phase windings. Unless specified otherwise, the descriptionbelow is for a single-phase AC input produced by the above describedstator 130.

With reference to FIG. 13, the rectifier/regulator 500 includes a bridgerectifier 505. The bridge rectifier includes diodes D5 and D14 formingthe upper portion of the bridge rectifier 505, and silicon-controlledrectifiers SCR1 and SCR3 forming the lower portion of the bridgerectifier 505. Diodes D4 and D15 provide an input or control signal forcontrolling the bridge rectifier 505. First filter 510 (resistor R29 andcapacitor C4) filters the control signal provided to silicon-controlledrectifier SCR1 and second filter 515 (resistor R19 and capacitor C29)filters the control signal provided to silicon-control rectifier SCR2.Filtering the control signals provided to the silicon-controlledrectifiers SCR1 and SCR2 prevents the silicon-controlled rectifiers SCR1and SCR2 from being too sensitive. During operation of the bridgerectifier 505, the rectifier 505 receives the high-voltage AC inputgenerated by the stator 130 via inputs W9 and W3, rectifies andregulates the AC input in response to the control signals being providedto the silicon-controlled rectifiers SCR1 and SCR3, and provides ahigh-voltage DC output. The high-voltage DC output is stored oncapacitors C6 and C3, which act as a DC bus. For the embodimentdescribed, the high-voltage DC output is preferably 150-VDC. But,depending on the load attached to the power circuitry 135, the DC busmay fluctuate between 100-VDC and 150-VDC. If the stator 130 is athree-phase stator, then the bridge rectifier includes input W4, diodeD7, silicon-control rectifier SCR2, and third filter 520 (resistor R30and capacitor C5).

The rectifier/regulator 500 further includes a voltage monitor 525 and atrigger circuit 530. The voltage monitor 525 includes opto-isolator U2,precision voltage reference U1, zener diode D9 and resistors TU8, R31and R32. The trigger circuit 530 includes zener diodes D1 and D2,metal-oxide semiconductor field-effect transistors (MOSFETs) Q1 and Q2,opto-isolator U8, diac Q11, capacitors C1 and C2, and resistors R2, R3,R4, R5, R6, R8, R9, R10 and R27. The voltage monitor 525 and the triggercircuit 530 control the bridge rectifier 505 to provide a continues busvoltage between, 130-VDC and 150-VDC. Specifically, the trigger circuit530 acts as a phase control that activates the silicon-controlrectifiers SCR1 and SCR3 depending on the amount of power required to beadded to the DC bus. For example, if the voltage monitor 525 senses avoltage on the DC bus greater than 150-VDC, then the trigger circuit 530triggers the silicon-controlled rectifiers SCR1 and SCR3 later in thephase of the high-voltage AC input. This results in less energy beingprovided to the DC bus and, therefore, a lower voltage. Similarly, ifthe voltage monitor 525 senses a voltage on the DC bus less than150-VDC, then the trigger circuit 530 causes the silicon-controlledrectifiers SCR1 and SCR3 to activate sooner in the phase of thehigh-voltage AC input. This results in more energy being provided to theDC bus and, consequently, a higher voltage. The voltage monitor 525 andthe trigger circuit 530 attempt to regulate the DC bus voltage toapproximately 150-VDC. However, depending on the load attached to thepower circuitry 135, the DC bus voltage may range between 130-VDC and150-VDC. Of course, other voltages may be used for the DC bus.

The rectifier/regulator 500 further includes a low-voltage DC powersupply 535. The low-voltage DC power supply 535 includes zener diodeD10, capacitor C7 and resistors R33 and R34. The low-voltage DC powersupply 535 receives the high-voltage DC output and produces alow-voltage DC output. For example, the low-voltage DC signal may be15-VDC. Of course, other low-voltage DC outputs may be used.

Referring back to FIG. 12, the power circuitry 135 further includes abridge circuit 540. For the embodiment shown (FIG. 14), the bridgecircuit 540 is an H-bridge circuit. The bridge circuit 540 includesfirst branch 545 (MOSFETs Q9, Q10 and Q14, resistor bridge 42, andresistor R22), second branch 550 (MOSFETs Q7, Q8, and Q15, resistorbridge R20, and resistor R25), third branch 555 (MOSFETs Q5, Q6, andQ12, resistor bridge R21, and resistor R14), and fourth branch 560(MOSFETs Q3, Q4, and Q13, resistor bridge R13, and resistor R18). Thebridge circuit 540 receives the high-voltage DC bus, and produces a120-VRMS, 60-Hz AC output at terminals W1 and W2 in response to aplurality of drive signals 1aOUT, 1bOUT, 2aOUT and 2bOUT. Of course,other output voltages and frequencies (e.g., a 100-VRMS, 50-Hz ACoutput) may be produced. In addition, other bridge circuits may be used.For example, the embodiment shown in FIG. 14 has three MOSFETs in eachbranch. For a different embodiment, the number of MOSFETs may vary(e.g., two MOSFETs) depending on the capacity of the MOSFETs and themaximum expected current generated by the bridge circuit 540.

The drive signals 1aOUT, 1bOUT, 2aOUT and 2bOUT, and floating groundsignals 1aSOURCE and 2aSOURCE are provided to the bridge circuit 540 bydriver circuits 565 and 570 (FIGS. 12, 15 and 16). First driver circuit565 (FIG. 15) includes driver U5, capacitors C14, C15, C16, C17, C18,resistors R44, R50 and R51, and diode D12. The first drive circuit 565drives the first and second branches 545 and 550 (FIG. 14) with thesignals 1aOUT, 1bOUT and 1aSOURCE in response to gate signals GATE1 aand GATE1 b (discussed below). The second drive circuit 570 includesdriver U4, capacitors C9, C10, C11, C12, C13, resistors R41, R52 andR53, and diode D11. The second drive circuit 570 (FIG. 16) drives thethird and fourth branches 555 and 560 with the signals 2aOUT, 2bOUT and2aSOURCE in response to the signals GATE2 a and GATE2 b (discussedbelow).

During operation of the bridge circuit 540 and the first and seconddriver circuits 565 and 570, an output signal is generated at terminalsW1 and W2 (FIG. 14). The output is a pulse-width-modulated (PWM) signalhaving a frequency of approximately sixty Hz and a voltage ofapproximately 120-VRMS. Specifically, the first and second drivers 565and 570 drive the MOSFETs Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q12, Q13, Q14and Q15, to produce a PWM 120-VRMS, 60-Hz signal at W1, W2. Each cycleincludes a square wave that is PWM to produce the required RMS voltage.The width of each half cycle is widened or narrowed depending on the DCbus voltage. If the DC bus voltage is low, then the width of each halfcycle is widened. Conversely, if the DC bus voltage is high, then thewidth of the half cycle is narrowed. Thus, based on the drive signalsprovided to the bridge circuit 540, the output of the bridge circuit 540maintains a relatively constant 120-VRMS, 60-Hz signal at outputs W1 andW2.

The output signals 1aOUT, 1bOUT, 1aSOURCE, 2aOUT, 2bOUT, and 2aSOURCEresult from gate signals GATE1 a, GATE1 b, GATE2 a and GATE2 b. The GATEsignals GATE1 a, GATE1 b, GATE2 a, and GATE2 b are generated by amicroprocessor (discussed below). The first and second drivers U4 and U5translate the gate signals GATE1 a, GATE1 b, GATE2 a and GATE2 b to15-VDC drive signals (i.e., 1aOUT, 1bOUT, 2aOUT and 2bOUT). The 15-VDCdrive signals are necessary to drive the MOSFETs Q3, Q4, Q5, Q6, Q7, Q8,Q9, Q10, Q12, Q13, Q14 and Q15. The signals 1aSOURCE and 2aSOURCEprovide a floating reference to the bridge circuit 540.

The bridge circuit 540 shown in FIG. 14 includes a shunt resistor R11.The shunt resistor R11 is a power shunt for measuring the output currentof the bridge circuit 540. The shunt resister R11 is used to determineif an overload current is present i.e., if an operator is applying toolarge of a load to the bridge circuit 540. If too large of a load ispresent, the microprocessor (discussed below) narrows the pulse width ofthe 120-VRMS, 60-Hz output so that it cannot deliver too large of acurrent through the bridge circuit 540. The current measurement signalSHUNT is provided to a current limit circuit 575 (shown in FIG. 17). Thecurrent limit circuit 575 includes operational amplifiers U3A, U3B,resistors R1, R35, R36, R37, R38, R39, and R40, and capacitors C8 andC26. The operational amplifiers U3A amplifies the signal SHUNT, and theoperational amplifier U3B acts as a comparator between a referencesignal and the amplified SHUNT signal. The reference signal is formed byresistors R39 and R40. The reference signal is set such that the peakcurrent created by the bridge circuit cannot exceed a maximum peakcurrent (e.g., forty-five amps). The maximum peak current is the maximumsafe current the MOSFETs Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q12, Q13, Q14and Q15 can handle without burning out. The current limit signal iLIMITis provided to the microprocessor (discussed below).

As shown in FIGS. 12 and 18, the power circuitry 135 includesmicroprocessor U7. The microprocessor U7 receives and executes asoftware program from memory. Based on the inputs provided to themicroprocessor U7, the microprocessor controls the driver circuits 565and 570 with gate signals GATE1 a, GATE1 b, GATE2 a and GATE2 b.Specifically, the software determines the pulse width of each half cyclegenerated by the bridge circuit 540 based on the inputs provided to themicroprocessor U7. For example, one of the input signals is the currentlimit signal iLIMIT. If the signal iLIMIT signifies that the current tothe load is excessive, the microprocessor U7 controllably reduces thewidth of the PWM output signal.

As shown in FIGS. 12 and 18, the power circuitry 135 further includes avoltage feedback circuit 580. The voltage feedback circuit 580 includesresistors R48 and R49 and capacitor C23. The voltage feedback circuit580 reduces the voltage from the DC bus to a 0-VDC to 5-VDC signal. Thefeedback from the DC bus informs the microprocessor U7 what the DCvoltage is on the high-voltage bus.

As shown in FIGS. 12 and 18, the power circuitry 135 further includes athermal shut down circuit 585. The thermal shut down circuit 585includes a thermistor R15, a capacitor C24 and a resistor R12. Thethermistor R15 is mounted near the MOSFETs Q3, Q4, Q5, Q6, Q7, Q8, Q9,Q10, Q12, Q13, Q14 and Q15, and senses the temperature generated by thebridge circuit 540. If the bridge circuit 540 generates an excessivetemperature, thermistor R15 conducts and generates a high-logic signalTRIP. The microprocessor U7 receives the high-logic signal TRIP andstops producing the 120-VRMS, 60-Hz output. An example temperature maybe 90-100 degrees Celsius. The higher the temperature gets, the soonerthe thermal shut down circuit 585 generates the high-logic signal TRIP.

As shown in FIGS. 12 and 18, the power circuitry 135 further includes anoscillator XT1 for providing an oscillating signal to the microprocessorU7 and a voltage regulator U9 for generating a 5-VDC VCC signal. Thepower circuitry 135 further includes a deactivate circuit 590 includingresistors R63 and R64, capacitors C25 and C27 and optoisolator U6. Thedeactivate circuit 590 receives a 12-VDC blade signal 12BLADE or a12-VDC input signal from terminals W7 and W8. When no twelve-volt signalis present, the microprocessor U7 prevents the 120-VRMS, 60-Hz signalfrom being generated. Alternatively, if the 12-VDC signal is presentthen the power circuitry 135 may generate an output. For example, if thegenerator 110 is mounted on a lawnmower, then the 12-BLADE signalinforms the microprocessor U7 whether the blade is running. If the bladeis rotating, the power circuitry 135 does not produce an output.

As shown in FIGS. 12 and 18, inputs W5 and W6 receive a signal from apower switch. The power switch is an on/off switch that the operatoractivates and deactivates for controlling the power circuitry 135. Inthe embodiment described herein, the power switch has to be turned ONfrom the OFF position in order for the power circuitry 135 to generateany power. For example, if an operator turns the engine on while thepower switch is already in the ON position, then the microprocessor U7does not allow an output from the power circuitry 135. This prevents anaccidental output from being generated. In order to enable the powercircuitry 135, the switch must be moved to the OFF position and thenreturned to the ON position.

In operation, when an operator starts the vehicle 100, the engine 110causes the drive shaft 115 to rotate and, consequently, theflywheel/rotor apparatus 125 to rotate. The flywheel/rotor apparatus 125uses its inertia to smooth-out the rotation of the drive shaft 115. Thisallows the engine to run evenly for driving the rotation of the wheels105. In addition, the magnetic fields produced by the rotor magnets 380interact with the stator resulting in a current being generated in thefirst and second wires 310 and 320. The current produced in the secondwire 320 is provided to the engine ignition system and/or the enginebattery, and the current produced in the first wire 310 is provided tothe power circuitry 135. The current that is provided to the powercircuitry 135 is first regulated to produce a high-voltage DC output anda low voltage-DC output. The high-voltage DC output is stored in astorage device (e.g., capacitors C3 and C6). The storage device acts asa DC bus voltage. The low-voltage DC signal is provided to, among otherthings, the VCC regulator for generating a five-volt VCC signal. The5-VDC VCC signal is provided to the microprocessor U7.

When the microprocessor U7 receives the 5-VDC VCC signal, themicroprocessor U7 loads a software program from memory into themicroprocessor U7. As shown in FIG. 19 and at step 710, the softwareinitializes the microprocessor U7 and sets one or more interrupts. Theinitializing of the software includes initializing a main timer andsetting an error flag ERR to high. The error flag ERR remains high untilthe software validates everything is properly running. The interruptsinclude a periodic interrupt (e.g., a 260 microsecond interrupt), and aninterrupt occurring on the rising edge of the current limit signaliLIMIT. Of course, other interrupts, timers, and error flags may beincluded.

At step 715, the software increase the main timer until an interruptoccurs. The interrupt may be the periodic interrupt or an interrupt dueto the current limit signal iLIMIT. Once an interrupt occurs then thesoftware proceeds to perform an interrupt service (step 720).

At step 720, the software performs the interrupt service. In generalterms, the software determines the cause of the interrupt and performsnecessary actions based on the cause. As shown in FIGS. 20 a and 20 b,if the interrupt is due to a high current (step 725), then the currentbeing conducted through the MOSFETs is too high. When this occurs, thesoftware sets a LIMIT flag to high (step 730). Setting the LIMIT flag tohigh informs later software modules to limit the amount of time theMOSFETs are on. Limiting the amount of time the MOSFETs are on reducesthe amount of power and, consequently, current being conducted throughthe MOSFETs.

If the interrupt was due to a periodic interrupt (step 725), then thesoftware proceeds to step 735. At step 735, the software samples theiLIMIT signal to determine if the amount of current being transmitted bythe MOSFETs is within the desired limit. If the current is within limit,then the software sets the LIMIT flag to low (step 740). If the currentis not within limit, then the software proceeds to step 745.

At step 745, the software determines whether the interrupt was aperiodic interrupt. If the interrupt was a periodic interrupt, thensoftware proceeds to step 750. Otherwise, the software returns from theinterrupt service.

At step 750, the software resets the main timer for counting the nextinterrupt. At step 760, the software calls a HOTSub subroutine. TheHOTSub subroutine checks whether the signal produced by the thermal shutdown circuit is high. If the signal is high, then the MOSFETs aregenerating too much heat signifying that too much power is beinggenerated. If the temperature is too hot, then a HOT counter isincreased. If the temperature is satisfactory, then the HOT counter isdecreased. If the HOT counter reaches a maximum count (e.g., fifteen),then the OUTPUT flag is set to low and the ERR flag is set to high.Setting the OUTPUT flag to low prevents gating of the MOSFETs (discussedbelow) and the ERR flag informs the processor a possible error isoccurring. In addition a display may be used to inform the operator thatthe generator is too hot. The HOT counter includes a counting range(e.g., between zero and fifteen). Thus, the HOT counter allows the powercircuitry 135 to generate some heat. But if too much heat is beinggenerated for too long of a period of time, then the microprocessor U7prevents electricity from being generated.

At step 765, the software determines whether the OUTPUT flag is set tohigh. If the OUTPUT flag is set to high, then the software has themicroprocessor U7 generate the gating signals GATE1 a, GATE1 b, GATE2 a,and GATE2 b for controlling the bridge circuit 540 (step 770). Thegating signals control the first and second drivers U4 and U5, whichdrive the bridge circuit 540. The gating signals are set by the softwaredepending on the results of the PWSub subroutine (discussed below). Ingeneral, the software controls the gating of the microprocessor U7 basedon the sensed bus voltage. The microprocessor U7 determines the pulsewidth PWM of the 120-VRMS, 60-Hz signal. If the OUTPUT flag is low (step765), then the microprocessor U7 does not generate gating signals andthe generator does not generate the 120-VRMS, 60-Hz signal (step 775).

At step 778, the software calls a DCSub subroutine, a VPWSub subroutineand a VOUTSub subroutine. The DCSub subroutine calculates the value ofthe DC bus voltage sensed by the voltage feedback circuit 580. TheVPWSub subroutine determines the average value that each MOSFET is on.Based on the average value, the pulse width may be calculated. TheVOUTSub subroutine calculates the RMS voltage being generated by thepower circuitry 135. The RMS voltage is calculated using the sensed DCbus voltage and the calculated pulse width. For example, the RMS voltagemay be calculated using a sum of squares calculation. If the RMS voltageis too high or too low, the software can adjust the gating signals. Inaddition, if the voltage is less than 90-VRMS for thirty continuousseconds, then the OUTPUT flag is set to low and the ERR flag is set tohigh. Similarly, if the voltage is less than 50-VRMS for two continuousseconds, then the OUTPUT flag is set to low and the ERR flag is set tohigh.

At step 780, the software determines whether sixty-four interrupts haveoccurred. If sixty-four interrupts have occurred, then the softwareperforms an ONOFFSub subroutine, a BLADESub subroutine, and a PWSubsubroutine (step 785). These subroutines do not need to be performedevery interrupt. Of course, sixty-four is an arbitrary number and othercounters may be used. If sixty-four interrupts have not occurred (step780), then the software increases the interrupt counter (step 790) andreturns from the interrupt service.

The ONOFFSub subroutine determines whether the on/off switch forgenerating the 120-VRMS, 60-Hz signal is on. If the on/off switch is offthen it sets the ERR flag to low. Thus, the user has to “reset” thegenerator 120. For example, when the engine 110 first starts combusting,the generator 120 does not initially start generating power andaccidentally cause damage to an attached load. The operator must turnthe generator off and then on before the system will start generating.In addition, the software determines whether an initial DC bus voltageis greater than 120-VDC. If the DC bus voltage is greater than 120-VDC,then the software sets the OUTPUT flag to high. Thus, before the powercircuitry 135 generates an output, the DC bus voltage must be at least120-VDC. Of course, other voltages may be used.

The BLADESub subroutine determines whether either the blade signal orthe interrupt signal is set to high. If either are high, then the ERRflag is set to high and the output flag is set to low. For example, ifthe generator is mounted on a lawnmower, then the operator cannot havethe blade on and generate the 120-VRMS, 60-Hz signal at the same time.Similarly, for other vehicles, other interrupts may be used.

The PWSub subroutine uses the values calculated by the VOUTSub, VPWSuband DCSub subroutine to determine which gate signals should be activefor driving the bridge circuit. Once the calculation is performed, thesoftware resets the periodic interrupt count (step 795) and returns fromthe interrupt to step 715 (FIG. 19).

As can be seen from the above, the present invention provides a vehicleincluding a generator. Various features and advantages of the inventionare set forth in the following claims.

1. An apparatus comprising: an engine including a shaft having alongitudinal axis, and a housing having a structure; a stator includinga core and conductors disposed on the core, the core comprising a firstplurality of laminations defining a first inner surface surrounding thelongitudinal axis and comprising a first lamination, the first innersurface being disposed a first radius from the longitudinal axis in aradial plane, the first lamination having a first surface transverse tothe axis, the first surface having a first width in the radial plane, asecond plurality of laminations disposed adjacent to the first pluralityof laminations, the second plurality of laminations defining a secondinner surface surrounding the longitudinal axis and comprising a secondlamination disposed adjacent to the first lamination, the second innersurface being disposed a second radius from the longitudinal axis in theradial plane, the second radius being greater than the first radius, thesecond lamination having a second surface partially disposed adjacent tothe first surface and transverse to the axis, the second surface havinga second width in the radial plane, the second width being less than thefirst width; a rotor coupled to the shaft, at least a portion of therotor surrounding at least a portion of the core; wherein the firstlamination includes a shelf defined by the portion of the first surfacenot being disposed adjacent to the second surface in the radial plane,and wherein the shelf and a portion of the second inner surface define arecess; and wherein the structure of the housing extends into therecess.
 2. An apparatus as set forth in claim 1 wherein the core definesan aperture in the radial plane, and wherein the aperture is disposed inonly the first lamination of the first lamination and the secondlamination.
 3. An apparatus as set forth in claim 2 wherein the aperturereceives a fastener that interconnects the stator with the housing.